Not very pretty IMHO, but maybe something like:

use warnings;
use strict;

my $n = 5;

my $s = <<EOS;
line 1
line two
${ \ join "\n", ("repeated line tres") x $n }
line penultimate
line the last
EOS

print "[[$s]]";
[download]

Output:

c:\@Work\Perl\monks\Anonymous Monk\1197277>perl hiccup_here_1.pl
[[line 1
line two
repeated line tres
repeated line tres
repeated line tres
repeated line tres
repeated line tres
line penultimate
line the last
]]
[download]

(The explicit join statement | expression could become a call to a function returning any string.)